Regulating a 98xxx movement

Share:

I own 3 Vintage Collection watches with a 98xxx movement. When looking at the movements, and looking to all kinds of pictures of it, I notice that the "needle" is smack in the middle between Fast and Slow. As I read that this movement is rather difficult to regulate well, I wonder how this is done. I would expect that that needle would be moved towards Fast or Slow. However, that would not qualify as rather difficult. If regulation is done otherwise, what is the use of that long needle?

Kind regards,Paul

What you do may not be so important, but it is very important that you do it well. (my variation of a saying by Gandhi)

Basically, the regulation system, which is typical of most watches. involves a very minute shortening or lengthening of the balance spring. An index regulator moves one direction or another in order to very slightly lengthen or shorten the spring.

The Jones "arrow" or index uses an extra-long regulator and unlike most it is pointed in an opposite direction. By doing so, there is a greater arc, and therefore an ability to make even more very small changes.

The major problem with all regulation systems like this is that there's no easy way, except trial and error, to translate a movement to an exact timing difference. For example, moving the index 1/10th of a millimeter --itself not easy to do exactly-- doesn't easily translate to a precise change in seconds, such as say +1 second/day. There is a lot of fine timing involved. It is not like clicking an "off/on" or fast/slow" switch.

Second, the index can slightly move in use. Over time. it might loosen very slightly or be jarred. While that doesn't occur much or often, a slight move can translate into a timing difference.

The index regulation system is used in 98% of fine watches, with variances in design. Lately, for Calibre 51xxxx watches especially, IWC has switched to a "free-sprung" system. This system is more sophisticated and seldom gets out of whack, but it much more difficult to regulate initially. It basically involves no index or needle, but instead weights placed on the rim of the balance, to increase or decrease its inertia (which translates to slightly slower or faster, respectively). The weights are screwed in the rim and can be slightly screwed in or out. But, again, a slight twist of a screw doesn't translate to an exact timing difference. Patek and Rolex also use free-sprung balances.

As you can hopefully see, adjustment is not easy to accomplish within narrow and precise timing parameters, and to my thinking is as much an art as a science. You also can Google "Walt Odets" for articles on watch regulation.

Today, and also in the past, I read some articles about regulating. If I am allowed to summarise it, partly repeating Michaels explanation, there are two ways to do it:- shortening or lengthening the balance spring, with a swan neck device, or in case of the 98xxx movement, with the Jones arrow. I guess that is where the words Fast an Slow give an indication what to do.- turning the screws in the rim of the balance wheel. The 98xxx movements has these screws too. I really can imagine this operation is very complicated.

I guess, the latter method is used for the 98xxx movement. However, if this is true, what is the function of the Jones Arrow, and those words Fast and Slow? If the arrow is not meant to be used for this purpose, it could have been a lot smaller, or even non existent. Is it supposed to offer an alternative method that in reality is not used?

Kind regards,Paul

What you do may not be so important, but it is very important that you do it well. (my variation of a saying by Gandhi)

The screws on the balance wheel also can be used for consistency, like truing a wheel so that it spins well. That is the traditional purpose, rather than changing the speed. On the Cal. 98xxx movement the primary adjustment is through the Jones arrow or regulator.

Also, as a technical note, shortening or lengthening the balance spring does not usually involve a Swan's neck device. That really is a spring with screws that allows the regulator to be moved, and then stay fixed. within narrow tolerance. Often, a simple screw device works fine --like those used in Cal. 89 or 85xx vintage movements. There's even some early discussion in the archives about using "snails" on some Cal. 52 pocket watch movements. Swan's Necks just look pretty, although they work relatively well also.

MF Wrote:On the Cal. 98xxx movement the primary adjustment is through the Jones arrow or regulator.

OK, this point is clear, I think it makes sense because of the Fast and Slow: thank you, Michael. But that makes me come back to my original observation, that the arrow on my watches and those I saw on pictures, are all exactly in the middle between Fast and Slow. Is this pure coïncidence? I cannot believe that by regulating all these watches all those arrows would end up in the same position. It was only this observation that made me start this thread. Any explanation on this?

By the way, using the screw on the swan neck makes adjusting or regulating excactly a bit easier than moving the arrow, but that has no bearing on my question. If the movement had used the swan neck I would never have been able to make this observation, though.

Kind regards,Paul

What you do may not be so important, but it is very important that you do it well. (my variation of a saying by Gandhi)

lndblr Wrote:Someone correct me if I am wrong, but I still think that the pointer is calibrated to the middle once the movement has been regulated.

If possible, that makes sense and explains the phenomenon that Paul observes on all his watches with this movement.

Yes, that makes sense, quite clever. But it also makes the arrow an unnecessary attribute, as you then can regulate the movement without the arrow. If the arrow would serve as a kind of cap, then that cap could be mutch smaller. In that sense the arrow would then more be there as an ornament: a bit deceiving. This I am not quite willing to believe, I am sure the arrow in Jones' time really served a purpose that it probably serves today.

Gee, in a world full of problems this one really is minute. I know I know not enough about watches, but when I encounter something like this I just want to know, sorry.

Kind regards,Paul

What you do may not be so important, but it is very important that you do it well. (my variation of a saying by Gandhi)

I'm sorry, Paul, you're just incorrect. The movement when adjusted then shows the center position. If it goes to fast or slow, the "arrow" or needle is moved to adjust rate. You'll see pocket watches in which the regulator index has been moved one way or the other, way after it was initially centered.